What does the line equation calculator do?

It builds the slope-intercept equation y = mx + c from two points, or from a slope and one point, showing the steps.

What happens with a vertical line?

For a vertical line where x1 equals x2, the equation becomes x = constant and the slope is undefined.

Yes, it is free to use with no signup.

Slope m is found from (y2 - y1) / (x2 - x1), then c is found using y - y1 = m(x - x1).

Two ways: give two points in A, slope and one point in B — both build the slope-intercept equation y = mx + c with steps.

x₁

y₁

x₂

y₂

Slope (m)

Point x

Point y

Choose method A (two points) or B (slope and one point) at the top.
Fill in the coordinates or the slope value — the equation updates automatically as you type.
Read the slope-intercept equation y = mx + c, with each working step shown.
For a vertical line (both x values equal), the tool returns x = constant, since the slope is undefined.

Two different points always define a line, but they must not be identical — equal points give no direction.
The slope m tells you steepness: positive slopes rise left to right, negative slopes fall.
Use the steps shown to learn the method; the same slope-intercept form appears in school exams.

Note: Slope m = (y₂−y₁)/(x₂−x₁). Then c is found from y − y₁ = m(x − x₁).